...found a couple of other pics, thought I would put them up.
The felt padding used was from a craft store, lightweight...anything heavy will probably not work.

There are a few tight places on the box I have, the rifle fits very snug side to side, and I had to shave off a little on the block below the mag well for the buttstock to fit once the felt was added.

I used regular carpet tacks to keep period looking. Be aware that these tacks come in different sizes, I used a #4 any thing to big will probably split the pine wood....so be careful if you decide to go that route.

Make sure if you use any kind of a tack/staple that it is down into the pad far enough that it will not come in contact with the finish of the metal or wood surfaces.

The light grey tabs in the magazine slots are pull tabs to get the mag out.

You can see in this photo there is felt added to the bottom of the wood that secures the buttstock, in this case multiple layers (folded) were used to add thickness...tacks were only placed on the corners to "puff " out the felt.